A nailing machine, such as a nail gun, starts operation by means of synergistic combination of operation for activating a trigger placed in the vicinity of a handle and operation for pressing a lower end of a start lever located in the vicinity of an ejection section at an exit, from which a fastener such as a nail is fired, against a material subject to driving action (hereinafter called simply a “material”), such as wood. A nail in the ejection section is fired from the ejection section. The lower end of the start lever is located in the vicinity of the ejection section and pressed toward a bottom dead center by means of a spring that is supported so as to be movable between the bottom dead center at a leading end of the ejection section and the top dead center at a base end of the ejection section. Before operation of the nailing machine, the start lever is situated at the bottom dead center.
When driving operation is performed while nails are empty, the life of the nail gun is shortened, and an impact mark resultant from firing of a nail may also be left on the material, which will impair a finish. As described in Japanese Patent Number 3209032, in order to prevent such no-load firing operation, a protuberance provided at a leading end of a feeder that feeds nails to the ejection section is engaged with an engagement section of the start lever located at the bottom dead center when nails in a magazine becomes empty or comes to a predetermined number or less, thereby hindering movement of the start lever to the top dead center. The nail gun is configured such that, when movement of the start lever to the top dead center is hindered, the gun cannot be activated.
However, in the configuration described in connection with Japanese Patent Number 3209032, the amount of engagement of the engagement section with the protuberance provided at the leading end can be ensured merely to an extent that is equal to or smaller than the width of a nail. Therefore, in the case of a nail having a small width, such as a finishing nail, a sufficient amount of engagement cannot be ensured, and there has arisen a case where a no-load firing prevention mechanism fails to operate at a predetermined number of nails.
A configuration described in connection with Japanese Patent Number 3209032 is directed toward a complicate structure, wherein the width of a nail is amplified, to thus increase an amount of engagement of the protuberance located at the leading end with the engagement member. However, nails are mass-produced and involve many errors in width, and hence the errors are also amplified. When control is performed on a per-nail basis, faulty operation arises, which sometimes results in occurrence of no-load firing.